Is this really correct?

[Sparky83]

Hi guys,

On a forum i often go on someone was asking about the MEB to there gas pipe as the gas engineer had pointed out that there was bonding to both side of the gas meter.

Someone asked this question...

Aren't gas mains plastic too? What is the earthing for, to protect those inside the property from an issue that causes the pipework to become live?


Somebody whom says they are an electrician said the following...

its to stop external influences affecting your metal work essentially, nowadays most incoming gas/water bonds are plastic and don't need the equipotential bonding to them but most sparkies do it anyway, just disconnect the before clamp wire and put it in the post clamp terminal, easy job and should take 2 mins. nothing will happen when you remove it, just make sure its tight enough not to pull out and the clamp should not spin on the pipe either

Now is this correct? As im pretty sure that you always need the MEB to be in place?

I did question this with him and his reply about did he mean supps was...

main bonds too, i know it seems crazy to me too, it come up on my last nic inspection i went to.

he asked why i bonded main earth and water when they was plastic incoming. if its not metal incoming into the property the the metal work is inside is classed as supplementary, (not required now) he then proceeded to ask me how i would get a shock from metal work if it wasn't even connected to the "installation" with so many instances where continuity cannot be obtained on all pipe work then there should never be a potential difference between materials. hence no bonds no difference. obviously all circuits in said install have to be 30ma rcd protected

(again im no lecturer but those who have niceic inspections know how ---- they can be, so only going on what im told)

Hope it makes sense, Any thoughts on the above?

 

[Darkwood]

Really DW?

I would say that if your start bonding metal work that wasn't an extraneous conductive part then you more likely to make that piece of metal live during a fault. We after all don't bond metal door frames, windows etc, as they have no contact with earth, and so bonding a metal pipe within an installation, that as no connection with earth, ie main pipe coming in plastic, but internal installation is copper, is IMO not needed.

Of course it is always best to check if the pipe is an extraneous conductive part, but if it isn't it don't need bonding

As mentioned in other post page 42 green OSG states 'where there is plastic incoming service and a metal installation within the premises main bonding is recommended unless it has been confirmed that any metallic pipework within the building is not introducing earth potential.

This is one of those regs that can be misread in my mind, as a golden rule always bond Gas/Water regardless of incoming pipe unless internal pipework is also plastic, consider a live wire under the floor touches a water pipe which has no bonding and has incoming plastic supply... there will then be a floating PD of 230v from say your tap and a adjacent cooker's metal work, its no rocket science to work out the consequences of this situation as ive been called out to exactly this issue, with regards to doors and windows in metal... their was alot of confusion many years ago regarding said bonding and at one point it was necessary but this was soon shelved as the likelyhood of windows and doors becoming live and a risk to safety was neglegible as well as been screws/bolted to the building mass too which would give a easier earth path than joe bloggs opening door.
Yes agree circumstances do exist where you dont need to bond gas/water if incoming plastic and metal internal but it would require thorough checking that it dosnt introduce earth potential and is prone to other trades altering their installs and making bonding a requirement.... so to sum up i reckon its best to do it regardless of incoming pipe.

 

[Des 56]

But still I can't see how bonding a non extraneous part, is making the installation safer.

The only reason I can think of why they give this advise and it still makes no justification for doing so

,is,is,is,is and I have just thought about it,and even my thoughts come to a full stop

So my conclusion must be,minds better able than my own have made this assessment and who am I,but a wilting spark to be so bold and argue the point

believe me Des I've tried to get all those in place, but she won't stand still long enough.
Come now,there are less brutal ways of divorcing the dear one

 

[Engineer54]

As mentioned in other post page 42 green OSG states 'where there is plastic incoming service and a metal installation within the premises main bonding is recommended unless it has been confirmed that any metallic pipework within the building is not introducing earth potential.

This is one of those regs that can be misread in my mind, as a golden rule always bond Gas/Water regardless of incoming pipe unless internal pipework is also plastic, consider a live wire under the floor touches a water pipe which has no bonding and has incoming plastic supply... there will then be a floating PD of 230v from say your tap and a adjacent cooker's metal work, its no rocket science to work out the consequences of this situation as ive been called out to exactly this issue, with regards to doors and windows in metal... their was alot of confusion many years ago regarding said bonding and at one point it was necessary but this was soon shelved as the likelyhood of windows and doors becoming live and a risk to safety was neglegible as well as been screws/bolted to the building mass too which would give a easier earth path than joe bloggs opening door.
Yes agree circumstances do exist where you dont need to bond gas/water if incoming plastic and metal internal but it would require thorough checking that it dosnt introduce earth potential and is prone to other trades altering their installs and making bonding a requirement.... so to sum up i reckon its best to do it regardless of incoming pipe.

I can see you getting slated for that comment by some here....lol!!

 

[Deleted member 9648]

As mentioned in other post page 42 green OSG states 'where there is plastic incoming service and a metal installation within the premises main bonding is recommended unless it has been confirmed that any metallic pipework within the building is not introducing earth potential.

This is one of those regs that can be misread in my mind, as a golden rule always bond Gas/Water regardless of incoming pipe unless internal pipework is also plastic, consider a live wire under the floor touches a water pipe which has no bonding and has incoming plastic supply... there will then be a floating PD of 230v from say your tap and a adjacent cooker's metal work, its no rocket science to work out the consequences of this situation as ive been called out to exactly this issue, with regards to doors and windows in metal... their was alot of confusion many years ago regarding said bonding and at one point it was necessary but this was soon shelved as the likelyhood of windows and doors becoming live and a risk to safety was neglegible as well as been screws/bolted to the building mass too which would give a easier earth path than joe bloggs opening door.
Yes agree circumstances do exist where you dont need to bond gas/water if incoming plastic and metal internal but it would require thorough checking that it dosnt introduce earth potential and is prone to other trades altering their installs and making bonding a requirement.... so to sum up i reckon its best to do it regardless of incoming pipe.

This is confusing bonding with earthing...the two are entirely different. If it was necessary to earth all metallic pipe within an equipotential zone the regulations would require a test of pipework to ensure continuity from the nearest to the furthest point in the building. No such test is required....If your purpose in bonding is also to earth metallic pipework,then clearly you have failed if you do not verify a low continuity through the entire system.

 

[Darkwood]

I can see you getting slated for that comment by some here....lol!!

At 40 im may be old Hat but we were taught its required to be done with the exception of all plastic pipe incoming and internal, ive witness circumstances where bonding hadn't been done and resulted in shock, even on incoming plastic, i believe all the regs and guidelines have done here is to show you there does exist circumstances when it wouldnt be necessary when incoming plastic and internal metal piping but they also cover it with a recommendation to be done, this will avoid others trades making alterations and leaving the pipework needing bonding where as it didnt require it before. I believe they have included this exclusion as circumstances can exist where its not needed but more for your knowledge rather than for you to not bother doing it, regulations are changed and ammended all the time and its probably because select ppl made this point that situation can exist where not needed so they had to include it rather than leave it out.

Im good for debate and im also happy to stand corrected and admit it but i enjoy banter and different views it throws up... with all respect i learnt indepth on the 15th edition and 20 yrs just keeping up with changes but without healthy debate ppl can become stubborn and set in there ways whether they are right or wrong.

 

[malcolmsanford]

DW what if we have a nail that goes exactly through a LINE conductor, but does not damage or touch the NEUTRAL/EARTH conductors ................ There is just a good a chance that will become live as your pipe.

To me it is risk assessment, IMO there is more of a danger that you make the installation less safe by bonding metal work that are non extraneous conductive parts, that the scenarios we have mentioned.

I totally agree there is more danger in yours, than mine and a damaged cable under a floor in the bathroom can touch a pipe there and transfer down to a sink with someone touching across it, but there is also the danger of under a fault condition that pipe become live because you bonded it.

For me it is just the blanket if it plastic incoming, metal inside .....bond it .............regardless of what it is. I just think it takes the not thinking for ourselves away from us

 

[Darkwood]

DW what if we have a nail that goes exactly through a LINE conductor, but does not damage or touch the NEUTRAL/EARTH conductors ................ There is just a good a chance that will become live as your pipe.

To me it is risk assessment, IMO there is more of a danger that you make the installation less safe by bonding metal work that are non extraneous conductive parts, that the scenarios we have mentioned.

I totally agree there is more danger in yours, than mine and a damaged cable under a floor in the bathroom can touch a pipe there and transfer down to a sink with someone touching across it, but there is also the danger of under a fault condition that pipe become live because you bonded it.

For me it is just the blanket if it plastic incoming, metal inside .....bond it .............regardless of what it is. I just think it takes the not thinking for ourselves away from us

I agree it is risk asses' but not knowing your age here, i can remember niceic telling us to bond ceiling grid work, then following year not required, same with sinks etc ive seen some of these circumstances repeat more than once and at the time were regs, its seems to be less strict now but i can only assume the mass introduction of RCD on most circuits now means bonding is not the bees knees it once was and can be relaxed under certain circumstances. Im probably more set in my ways through experience where ive seen lack of such bonding result in someone getting nasty shock, now times are a changing and an RCD would have minimised said shock had it been reg's in them days.

 

[malcolmsanford]

Well mate i'm a bit older than you ............:arabia: .....................not as old as Tel though.

If you take my house the incomer is plastic to the SC. Then copper into the downstairs Bathroom, but then tee of into the sink and shower with plastic.

The copper goes on to kitchen where it was completely rerouted because we moved the boiler. It tees off into the kitchen in plastic but then carries on to the outhouses in copper.............so I could bond the that pipe.

We plastic up to the boiler upstairs. In kitchen though the pipework going upstairs is copper to the bathroom and the en-suites, we fed the riser from the plastic pipe, Now the en-suite is not been touched pipe wise so it's all copper, but the bathroom is tee off in plastic from the riser, and does the bath, shower handbasin etc. so plastic ok.

But unfortunately 2 bedrooms have vanity sinks and all these are still in copper that are teed of that plastic bathroom pipe ......................at this rate I would have BS 951 clamps everywhere.

I don't have main bonding because it is plastic incomer, and I IR every pipework in the outhouse and the bathrooms and none are extraneous conductive parts

 

[Sparky83]

Well mate i'm a bit older than you ............:arabia: .....................not as old as Tel though.

If you take my house the incomer is plastic to the SC. Then copper into the downstairs Bathroom, but then tee of into the sink and shower with plastic.

The copper goes on to kitchen where it was completely rerouted because we moved the boiler. It tees off into the kitchen in plastic but then carries on to the outhouses in copper.............so I could bond the that pipe.

We plastic up to the boiler upstairs. In kitchen though the pipework going upstairs is copper to the bathroom and the en-suites, we fed the riser from the plastic pipe, Now the en-suite is not been touched pipe wise so it's all copper, but the bathroom is tee off in plastic from the riser, and does the bath, shower handbasin etc. so plastic ok.

But unfortunately 2 bedrooms have vanity sinks and all these are still in copper that are teed of that plastic bathroom pipe ......................at this rate I would have BS 951 clamps everywhere.

I don't have main bonding because it is plastic incomer, and I IR every pipework in the outhouse and the bathrooms and none are extraneous conductive parts

Does it make any difference that all this pipework is linked by conductive water, so even if a live cable was to touch a metal pipe would it not effect someone touching the pipework that is the other end of a bit of plastic pipe?? If that makes sense???

 

[SPARTYKUS]

DW water is not as conductive as you might think. Great bit on it in kitchers book. It increases in conductivity with additives but not much.

 

[Geordie Spark]

Does it make any difference that all this pipework is linked by conductive water, so even if a live cable was to touch a metal pipe would it not effect someone touching the pipework that is the other end of a bit of plastic pipe?? If that makes sense???

I seem to remember reading of an experiment by Chris Kitching in his Inspection & Testing book in which he proved that water is not such a good conductor of electricity as some of us think it is.

The section in the book is the one about bonding plastic pipes ........ or not.

 

[Deleted member 9648]

I have to say I dont get the fixation with pipes being live,or becoming live....it just doesnt happen. Most of the copper sections of pipework will be earthed anyway by means of being in contact with conductive parts such as M/V's....immersion heaters....boilers etc. Often those who claim to be getting shocks off live pipes are mistaken anyway. Example.....I got called out to a property where a plumber was changing a boiler and claimed all the pipes were live,he refused to carry on until it was sorted. What in fact had happened was he had caused a bit of a flood draining down,and in an adjacent larder a cable dropped through a hole in the floor,this cable had been chewed by rodents and the live core was exposed. Water had reached the cable and plumber boy was kneeling in it,every time he touched a pipe,which was earthed,he got a shock via the water on the floor. Of course he assumed the pipes were live.

 

[SPARTYKUS]

He can't have, because Chris Kitcher said water doesnt conduct much. So that must be right :joker:

 

[Knobhead]

Just a note on the conductivity of water. I worked on a 1200V system that could be loaded up to 4000A. To keep the flexible conductors cool water was pumped though them. There was very close monitoring of earth leakage that would trip at 50mA. It never gave a problem.

 

[Des 56]

Just a note on the conductivity of water. I worked on a 1200V system that could be loaded up to 4000A. To keep the flexible conductors cool water was pumped though them. There was very close monitoring of earth leakage that would trip at 50mA. It never gave a problem.

Yep,Water has its uses mixing with those charged electrons

This is one that surprises the sceptics
'Hot-Washing' the Insulators of a 500,000 Volt Power Line! - YouTube